Public address loud speaker and clock system



2,839,607 PUBLIC ADDRESS LOUD SPEAKER AND cLock SYSTEM Filed Feb. 15, 1955 C. A. M KEE June 17, 1958 2 Sheets-Sheet 1 RE 0 n 5% VM m mnm A 6 PUBLIC ADDRESS LOUD SPEAKER AND CLOCK SYSTEM C. A. M KEE June 17, 1958 2 Sheets-Sheet 2 Filed Feb. 15, 1955 INVENTOR m m m4 5 United States Patent PUBLIC ADDRESS LOUD SPEAKER AND CLOCK SYSTEM Clarence A. McKee, Rye, N. Y. Application February 15, 1955, Serial No. 488,331

11 Claims. (Cl. 179-2) This invention is a public address loud speaker and clock system adapted for general application wherever such system is useful. For the purpose of concrete illustration, I will hereinafter disclose the same as used in a school.

In such environment, the several class rooms are each provided with a secondary clock connected in an electrical system with a central oflice, generally the otfice of the school principal, at which there is located a master clock which controls the clocks of the several class rooms. The system generally includes corrective adjuncts whereby the several secondary clocks are from time to time automatically checked or corrected, so that they all conform in timing to the master clock.

Modern schools are also equipped with a public address loud speaker system, entirely separate and apart from the clock system and this loud speaker system is generally of a type wherein the several rooms of the school may be addressed collectively or individually from the central oflice.

While these wholly separate and independent types of system operate satisfactorily, the installation, including wiring, etc., and the duplication of parts which must necessarily enter into wholly independent systems, requires the expenditure of large sums of money for their installation, as well as for the separate maintenance of the respective systems.

The object of the present invention is to provide a single system which may be far more economically installed than two systems and which is so constituted that it will perform the functions of both of the aforesaid systems in a simple, eflicient and economical manner.

Generally speaking, the present invention embodies a system wherein there is provided in each of the class rooms what may be termed generally an outlet box of the system. The outlet boxes of the several class rooms are connected by wiring, hereinafter described, to the central oflice and are there connected with a master clock and a public address loud speaker transmitting station. The outlet box in each of the class rooms is preferably set flush into the wall and is covered by a panel closing its front face and also preferably flush with the wall surface. On this panel are mounted an appropriate electric clock and loud speaker parts, both of which are electrically connected into the system at such individual outlet boxes, so that each class room has, in effect, one unit which serves both functions of telling time and public address. By the provision of such a system, I am able to minimize in parts and labor incident to the installation of units and wiring, conduit, and wall space,

and produce a system which will require minimum maintenance and permit installation at a nominal cost. Fur thermore, the panel in each individual class room is, in practice, of a neat and decorative nature and carries all the necessary local adjuncts of the system.

Features of the invention, other than those adverted to, will be apparent from the hereinafter detailed descrip- 2,839,607 Patented June 17, 1958 tion and appended claims, when read in conjunction with the accompanying drawings.

The accompanying drawings illustrate different practical embodiments of the invention, but the constructions therein shown are to be understood as illustrative only, and not as defining the limits of the invention.

Fig. l is a front elevation of a panel appropriate for use in the present system.

Fig. 2 is a section on the line 2-2 of Fig. 1, taken through both the panel and the outlet box associated therewith, the clock being shown in elevation.

3 is a back view of the panel with the outlet box removed.

Fig. 4 shows a system embodying the present invention utilizing a simplex type of clock correction.

Fig. 5 is a modified form of system embodying wire correction principles.

Referring to the drawings, 1 designates an outlet box, preferably of metal, adapted to be embedded in the wall of a room, such as the class room of a school. The front of this box is adapted to be closed by a panel 2 provided at its corners with screw holes through which screws may be passed into tapped openings in a flange 3 of the box so as to mount the panel in fixed position. The box has a closed back, top and bottom and is divided by a transverse partition 4 into upper and lower chambers of any appropriate size. That portion of the panel which overlies the upper chamber is provided with an opening adapted for the reception of a clock 5. This clock may be conveniently mounted for ready removal for the purpose of maintenance or otherwise by providing it at the upper portion of its back with a hook 6 adapted to be engaged with a slot 7' formed in the panel, as shown best in Figs. 2 and 3. With this mounting the clock will be suspended on the hook and may be removed at will, although ordinarily it appears to all intents and purposes to be an integral part of the panel.

I may employ in carrying out this invention any conventional secondary electric clock, preferably a synchronous motor clock, provided with electrically controlled connections for time correction. These clocks are well known and conventional and any one of them may be employed, as the clock per se forms no part of the present invention. The clock is provided with the usual face and hands, said hands being controlled and operated by a synchronous motor generally indicated at 8 in the drawings. These secondary clocks are also provided with a correcting relay comprising a clutch 1'] controlled by a coil 16, hereinafter referred to, and forming part and parcel of the conventional clock.

That portion of the panel which closes the front of the lower chamber box is provided with an appropriate grill 9 which is preferably ornamental in character and back of this grill is mounted a sound reproducing device, such as the loud speaker unit indicated generally by the reference character Ill. As shown in Fig. 2, the loud speaker unit includes a cone diaphragm 11 to which is afiixed an appropriate voice coil 12 with associated transformer 13. The lower chamber back of the grill has an acoustical lining 4a.

Each unit of the kind shown in Figs. 1, 2 and 3 may be incorporated in my system as a whole in different ways, Figs. 4 and 5 of which are exemplary. In any case the connections are made, as hereinafter stated, to a central oillce, generally in the same building.

Referring particularly to Fig. 4, the secondary clock mechanism embodies, generally speaking, a synchronous motor having an armature l4 operated by a field coil 15 and included in a circuit fed from any appropriate and convenient A. C. outlet. In practice, I prefer to mount an electrical outlet receptacle 0 directly within the upper chamber of the box and carry in the wires from the field *3- =3 coil 15 through a flexible cable C plugged into the receptacle O.

The secondary clock employed is also provided with the conventional correcting relay R. It embodies a coil 15, the armature of which is provided with a clutch 17, which, when the coil is energized, engages with a moving element of the clock mechanism to arrest movement thereof as may be required to effect the necessary correction. The clock mechanism, including the coil and corrective mechanism, are well known in the art and need no further description.

In the central office there is provided the usual master clock which embodies, among other adjuncts, a correcting mechanism indicated at 18 in Fig. 4. This master clock and correcting mechanism are conventional. Suffice it here to point out that the correcting'mechanism cozn prises a coil 19 operable upon a double pole switch At stated intervals the coil 19 is energized by the master clock and serves to close the double pole switches.

Also in the central ofiice is a public address sending station of any appropriate selective type which embodies as an inherent part the element indicated at 21 which includes movable switches 22, respectively operable over several contacts according to the particular type of program to be transmitted.

It is here pertinent to observe that the parts of Fig. 4 indicated at 5, 10, 18and 21 are all conventional. They have been separately and independently used in many schools. The present invention is not concerned with these individual and well known parts, but is directed, rather, to a novel and ei'licient method of interconnecting these parts in an integrated system. In the system employed in accomplishing this according to the wiring diagram of Fig. 4, a single cable is run from the central office to each room. This cable is shielded, as indicated at 23, and requires only two lines 24. One end of one wire 24 is connected to one terminal of the coil 13a of the loud speaker in-put transformer, while the other end of the same wire is connected to one winding 25a of an isolation transformer indicated at 25. The opposite ends of the other wire 24 are connected to the other termini of the same transformers. The shielding 23 is connected by a wire 26 to a center tap 27 of the coil 13a of the loud speaker input transformer 13 and includes the correcting relay coil 16 of the clock mechanism. The shield ing 23 is also connected through a wire 25 with one of the poles of the double pole switch 24 of the correcting mechanism 18 of the master clock. The other pole of the same switch is connected by a wire 29 to a center tap 3'!) on the coil 2.5a of the isolation transformer The coil 25a is provided with a companion coil 25b, the terminals of which are connected to the adjacent terminals of the switch mechanism 22. of the public address system transmitter element 21. The isolation transformer 25 may be located in any-suitable place, preferably at the central office where short wiring leads may connect it to the elements 18 and 21 of the system. Such being the case. it is important to note that, in order to accomplish all the results of the present invention in accordance with the system of Fig. 4, only a single cable is required with two wires therein from the central station to each room. This is in marked contradistinction to prior practice which requires the necessary wiring for two separate and independent systems.

In Fig. 5, I have shown a modified form of system which also uses but a single shielded cable with one additional wire therein. In this cable are enclosed two wires 31 which correspond to the wires 24. One end of each of these wires is connected to the coil 13a as in Fig. 4, while the other ends of the same wires are connected directly to the switch mechanism 22, the isolation transformer being omitted. The system shown in Fig. 5 is particularly intended for use in connection with clocks of the character wherein the correction is obtained through a direct wire to operate the clutch 17. To accomplish this result, I

incorporate within the cable the additional wire 32, one end of which is connected to one terminal of the correction relay coil 16, while the other end is connected to one terminal of switch of the corrective mechanism 33 which forms part of the usual master clock in conventional direct wire correction practice.

The operation of the system of Fig. 4 is as follows:

Under ordinary conditions the field coil 15 of the secondary clock 5 is energized from the receptacle 0 within the box 1 and operates on 60 cycle A. C. current. At appro at: intervals and for a predetermined duration, as determined by the master clock in the central ofiice, a current impulse is impressed upon the coil 19 associated with the master clock and, as a result thereof, a double pole switch 2-1? is closed thereby impressing upon the wire electric current, preferably of the 24 volt D. C. variety. One polarity of this current is grounded on the shielding 23, while the other polarity is impressed upon the coil 25a at the tap 3t) and, as a result, the current divides through the respective halves of the coil 25a and is fed through the lines 24 of the cable to the opposite ends of the coil 130. from which it is taken at the tap 27 and passed through the coil 16 of the correcting relay of the clock and thence back to ground on the shielding 23. The passage of current through this coil 16 functions in the conventional manner upon the conventional clock of the system to carry out the correcting function.

While this is transpiring the audible part of the system, whereby speech may be conveyed to any particular class room, is operative as and when required. In the event that an audible message is to be carried over the system, the switches 22 at the central sending station are adjusted to the proper stationary points of the element 21 to impress upon the system the desired program, such, for example, as a radio, phonograph, or voice music or message. As a result, current is passed through the coil 25b of the isolation transformer and is induced thereby to the coil 25a which is connected across the lines 24 and through these lines is passed to the coil 13a of the loud speaker in-put transformer 13. This current is induced into the circuit of the voice coil 12 and the speaker cone is actuated.

It will of course be understood that, while I have referred to the transmission of audible signals from a central station to the cone diaphragm till, this operation can just as well be in a reverse direction, the voice or other audible material to be transmitted being directed into the cone diaphragm Ill.

In Fig. 4, all of these operations are carried out through a cable embodying but two wires.

The operation of the system of Fig. 5 is as follows:

The clock 5 is connected to A. C. operating current, as described in connection'with Fig. 4, and functions in the conventional manner. Similarly the master clock at the central station periodically and within intervals of predetermined duration, impresses current upon the coil of the corrective mechanism 33 and, as a result, the switch forming part of said element is closed to impress 24 volt D. C. current through the wire 32 to the coil 16 of the corrective element of the secondary clock. The other side of this coil is grounded on the common side of the A. C. line which operates the synchronous motor. As a result of this current impulse, the clutch 17 acts upon the conventional clock in a conventional manner to carry out the corrective function.

While this corrective operation is being carried out, the audible part of the system remains operative to transmit audible sounds. When such transmission is to take place, the switches 22 of the element 21 at the central ofiice are closed in the same manner as described in Fig. 4, to place the lines 31 in communication with the transmitting mechanism at the central station. Audible sounds in the form of voice, phonograph or radio transcription are electrically transmitted through the lines 31 to one coil of the loud speaker in-put transformer 13, as in Fig. 4, and

audible signals issue from the cone diaphragm loud speaker 11. Audible signals may be transmitted in the opposite direction by speaking into the cone diaphragm.

It will be noted that in the system of Fig. 5, the wires 31 and 32 are contained within the same cable, the parts of the system being so arranged that the clock correction part of the system Will not in anywise interfere with the audible part of the system or vice versa.

A highly desirable and important practical feature of this invention resides in the fact that I may and preferably do use in practical installations electrical and mechanical instruments which are in themselves conventional and standard. It is not necessary therefore for me to make a special clock, or a special loud speaker, or special transmitting mechanism. In fact I may incorporate the system of this invention in a school or other place wherein the two old systems are already installed and are improperly operating, by simply installing a single new cable and connecting it up at each room and at the central oflice.

In this way an old system may be modernized by a more effective and efficient system, without requiring the substitution of new instruments at the termini of the cable. Furthermore in initially installing this invention as a new system, I may employ conventional instruments and thus materially save on the overall cost of installation.

Another important feature of this invention, from a practical standpoint, is that by providing a truly integrated system, the responsibility for its proper operation is established and maintenance by those skilled in its operation is facilitated. This feature of the invention is especially appealing to those in charge of schools and other institutions.

'1 have hereinbefore thus far described this invention as utilizing secondary clocks which have corrective relays therein. There is, however, on the market minute impulse, secondary clocks which are not dependent upon the operation of a synchronous motor, but simply embody a time train which is periodically moved forward every minute by passing an electrical impulse to the clock. The system of this invention may be employed for installations of this kind by merely substituting for the correcting relay in the clock the electromagnet of a conventional secondary minute impulse clock, so that each minute an electrical impulse is passed to the clock from the central station to advance the minute hands of the second clock, one minute.

In the foregoing detailed description, I have set forth this invention as employed in school installations, wherein it has been found to be of great utility. I wish it understood, however, that it is not limited to such application as it may be used in institutions of all kinds, interofiice communication, private homes and in any other environment where such a system will be of utility.

The foregoing detailed description sets forth the invention in its preferred practical forms, but the invention is to be understood as fully commensurate with the appended claims.

Having thus fully described the invention, what I claim as new and desire to secure by Letters Patent is:

1. In an installation wherein a master clock synchronizing means and sound transmitting mechanism are installed at a central station and an electrically operated secondary clock synchronizing means and a sound reproducing device are located at a distant station, the improvement which consists in electrically connecting the master clock synchronizing means and sound transmitting mechanism at the central station directly to the secondary clock synchronizing means and sound reproducing device respectively at the distant station through current conductors not exceeding three in number embodied in a single cable between said stations, said secondary clock synchronizing means and said sound reproducing device being simultaneously operable over said current conductors.

2. An installation according to claim 1, wherein the cable contains but two wires.

3. An installation according to claim 1, wherein the cable contains but three wires.

4. An installation according cable is a shielded cable.

5. An installation according to claim 1, wherein the cable is shielded and wherein the secondary clock synchronizing means is provided with a correcting relay with which the shielding of the cable is in circuit.

6. An installation according to claim 1, wherein the wiring between the sound transmitting mechanism at the central station and the sound reproducing device at the distant station includes an isolation transformer at the central station.

7. A system according to claim 1, wherein the cable is a shielded cable and forms a ground for one of the circuits thereby provided.

8. A composite system for simultaneous operation of clock synchronization means and communication means directly connected over common conductors comprising: a sound transmitting mechanism and a master clock synchronizing means at a central station, a sound reproducing device and a secondary clock synchronizing means at a distant station with an associated relay for the secondary clock synchronizing means, an electric circuit including a common return leading from the sound transmitting mechanism at the central station to the sound reproducing device at the distant station, said electric circuit including transformers at the central station and distant station, wiring connections between the master clock synchronizing means at the central station and said electric circuit, and wiring connections between the relay of the seconary clock synchronizing means at the distant station and said electric circuit.

9. A composite system according to claim 8, wherein said circuit is enclosed between the central station and the distant station in a single cable.

10. A composite system according to claim 9, wherein the cable constitutes the common return.

11. A composite system for simultaneous operation of clock synchronization means and communication means directly connected over common conductors comprising: a sound transmitting mechanism and a master clock synchronizing means at a central station, a sound reproducing device and a motor operated secondary clock synchronizing means at a distant station, an electric circuit including a common return leading from the sound transmitting mechanism at the central station to the sound reproducing device at the distant station, said electric circuit including transformers at the central station and distant station, wiring connections between the master clock synchronizing means at the central station and said electric circuit, and a corrective relay for the secondary clock synchronizing means at the distant station, said corrective relay being also interconnected into said electric circuit.

to claim 1, wherein the References Cited in the file of this patent UNITED STATES PATENTS 443,291 Mayrhofer Dec. 23, 1890 1,681,246 McCurdy Aug. 21, 1928 1,871,636 Trogner Aug. 16, 1932 2,052,055 Peterson Aug. 25, 1936 2,554,404 Grifiith May 22, 1951 2,647,360 Wagner Aug. 4, 1953 

